Add formula for blink1-tool

Was rejected in the past for not having release tags. They now have releases as tarballs on their github.

Has a homebrew-headonly equivalent formula, blink1 (https://github.com/Homebrew/homebrew-headonly/blob/master/blink1.rb), but I feel the formula is misnamed, as it is only building the blink1-tool executable. Not the other components of the project.